370 PERU. [cHAP. XVI. 
trace of organic structure. The powder has been analysed for 
me by Mr. T. Reeks; it consists of sulphates and muriates both 
of lime and soda, with very little carbonate of lime. It is known 
that common salt and carbonate of lime left in a mass for some 
time together, partly decompose each other; though this does 
not happen with small quantities in solution. As the half-de- 
composed shells in the lower parts are associated with much 
common salt, together with some of the saline substances com- 
posing the upper saline layer, and as these shells are corroded 
and decayed in a remarkable manner, I strongly suspect that 
this double decomposition has here taken place. ‘The resultant 
salts, however, ought to be carbonate of soda and muriate of 
lime; the latter is present, but not the carbonate of soda. Hence 
Iam led to imagine that by some unexplained. mens, the car- 
bonate of soda becomes changed into the sulphate. It is obvious 
that the saline layer could not have been preserved in any 
country in which abundant rain occasionally fell: on the other 
hand, this very circumstance, which at first sight appears so 
highly favourable to the long preservation of exposed shells, has 
probably been the indirect means, through the common salt not 
having been washed away, of their decomposition and early decay. 
I was much interested by finding on the terrace, at the height 
of eighty-five feet, embedded amidst the shells and much sea- 
drifted rubbish, some bits of cotton thread, plaited rush, and the 
head of a stalk of Indian corn: I compared these relics with 
similar ones taken out of the Huacas, or old Peruvian tombs, 
and found them identical in appearance. On the mainland in 
front of San Lorenzo, near Bellavista, there is an extensive and 
level plain about a hundred feet high, of which the lower part is 
formed of alternating layers of sand and impure clay, together 
with some gravel, and the surface, to the depth of from three to 
six feet, of a reddish loam, containing a few scattered sea-shells 
and numerous small fragments of coarse red earthenware, more 
abundant at certain spots than at others. At first I was inclined 
to believe that this superficial bed, from its wide extent and 
smoothness, must have been deposited beneath the sea; but I 
afterwards found in one spot, that it lay on an artificial floor of 
round stones. It seems, therefore, most probable that at a pe- 
riod when the land stood at a lower level, there was a plain very 
